The supergiant shell LMC 2. I. The kinematics and physical structure

S. D. Points, Y. H. Chu, S. Kim, R. C. Smith, S. L. Snowden, W. Brandner, R. A. Gruendl

Research output: Contribution to journalArticlepeer-review


LMC 2 has the brightest, most coherent filamentary structure of all known supergiant shells in the Large Magellanic Cloud. The optical emission-line images show active star formation regions along the western edge and long filaments to the east. ROSAT PSPC and HRI images show bright X-ray emission from within the shell boundary, indicating the presence of hot gas. Counterintuitively, neither high-resolution echelle spectra in the Hα line nor aperture synthesis H I 21 cm emission-line observations show LMC 2 to have the kinematics expected of an expanding shell. Rather, LMC 2 appears to consist of hot gas confined between H I sheets. The interior surfaces of these sheets are ionized by the UV flux of massive stars in the star formation regions along the periphery of LMC 2, while the heating is provided by outflows of hot gas from the star formation regions and by SNRs interior to LMC 2. We have compared LMC 2 to other supergiant shells in the LMC and in more distant galaxies. When the spatial resolution of our data are degraded, we find that LMC 2 resembles supergiant shells observed at a distance of 4 Mpc that have previously been interpreted as expanding shells. Therefore, great caution should be exercised in the analysis and interpretation of the kinematics of distant supergiant shells to prevent overestimates of their velocities and total kinetic energies.

Original languageEnglish (US)
Pages (from-to)298-323
Number of pages26
JournalAstrophysical Journal
Issue number1 PART 1
StatePublished - Jun 10 1999


  • ISM: bubbles
  • ISM: individual (LMC 2)
  • ISM: kinematics and dynamics
  • Magellanic Clouds

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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